Página 17 dos resultados de 100905 itens digitais encontrados em 1.450 segundos

‣ Device integration for silicon microphotonic platforms

Lim, Desmond Rodney
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 211 p.; 2081973 bytes; 2081727 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
66.504053%
Silicon ULSI compatible, high index contrast waveguides and devices provide high density integration for optical networking and on-chip optical interconnects. Four such waveguide systems were fabricated and analyzed: crystalline silicon-on-insulator (SOI) strip, polycrystalline silicon (polySi) strip, silicon nitride strip and SPARROW waveguides. The loss of 15 dB/cm measured through an SOI waveguide was the smallest ever measured for a silicon strip waveguide and is due to improved side-wall roughness. The TM mode of a single mode polySi strip waveguide with a 1:2.5 aspect ratio exhibited, surprisingly, smaller loss than the TE mode. Further, analysis shows that high index contrast waveguides are more sensitive to polarization dependent loss in the presence of surface roughness. Single mode bends and splits in both silicon and silicon nitride were studied. 0.01 dB/turn loss has been measured for 2 micron radius silicon bends. Polarization dependent loss was also observed; the bending loss of a TM mode was, as expected, much larger than that of a TE mode. The splitting losses for two-degree Y-split was 0.15 dB/split. A 1x16 multi-mode interferometer splitter occupied an area of 480 sq-microns and exhibited loss of 3 dB. ULSI compatible waveguide structures integrated with micro-resonators have been studied. Qs of 10000 and efficiencies close to 100% were achieved in high index contrast ring resonators and Qs of 100 million were achieved in microsphere resonators. A thermal and mechanical tuning mechanism was demonstrated for micro-ring resonators.; (cont.) In addition...

‣ Distributed coordination in network information theory

Schein, Brett E. (Brett Eric)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 231 p.; 1678843 bytes; 1678596 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
66.504053%
Constructing a large-scale wireless data network is spectacularly expensive. It is therefore important to understand how to efficiently utilize the physical infrastructure and available battery power, which are expensive system resources. Unfortunately, we currently understand very little about efficient communication in a distributed environment. In distributed wireless networks, there appears to be an interesting and complex trade-off between trying to take advantage of independent noisy signals at different relays and closely coordinating relay transmissions to a receiver. Designing the right structure for efficient communication, by choice of source transmission codebook and relay terminal processing, is the important and difficult problem on which we focus. We use an information theoretic framework to study several very simple multiple terminal networks, focusing exclusively on single source, single destination networks where communication must take place through intermediate nodes. Our goal is to determine how much data we can get reliably from source to destination, placing no importance on delay or computational complexity. The core problem then involves distributed detection at the intermediate nodes and coordination in relaying information to the destination.; by Brett E. Schein.; Thesis (Ph. D.)--Massachusetts Institute of Technology...

‣ Integrated model-based run-to-run uniformity control for epitaxial silicon deposition.

Gower, Aaron E. (Aaron Elwood)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 280 p.; 2853535 bytes; 2852814 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
66.504053%
Semiconductor fabrication facilities require an increasingly expensive and integrated set of processes. The bounds on efficiency and repeatability for each process step continue to tighten under the pressure of economic forces and product performance requirements. This thesis addresses these issues and describes the concept of an "Equipment Cell," which integrates sensors and data processing software around an individual piece of semiconductor equipment. Distributed object technology based on open standards is specified and utilized for software modules that analyze and improve semiconductor equipment processing capabilities. A testbed system for integrated, model-based, run-to-run control of epitaxial silicon (epi) film deposition is developed, incorporating a cluster tool with a single-wafer epi deposition chamber, an in-line epi film thickness measurement tool, and off-line thickness and resistivity measurement systems. Automated single-input-single-output, run-to-run control of epi thickness is first demonstrated. An advanced, multi-objective controller is then developed (using distributed object technology) to provide simultaneous epi thickness control on a run-to-run basis using the in-line sensor, as well as combined thickness and resistivity uniformity control on a lot-to-lot basis using off-line thickness and resistivity sensors.; (cont.) Control strategies are introduced for performing combined run-to-run and lot-to-lot control...

‣ Multiaccess and fading in communication networks

Yeh, Edmund Meng, 1971-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 163 p.; 771750 bytes; 771450 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
66.504053%
Two fundamental issues in the design of wireless communication networks are the interference among multiple users and the time-varying nature of the fading wireless channel. We apply fundamental techniques in information theory and queueing theory to gain insights into the structure of these problems. In a terrestrial cellular or space network, multi-user interference arises naturally as different users in the same cell or region attempt to transmit to the base station or satellite at the same time and in the same frequency range. We first examine the impact of this interference on the design of error correction codes for reliable data transmission. At the physical layer of the wireless network, the phenomenon of multi-user interference is captured by the multiaccess (many-to-one) channel model. The set of all data rates at which reliable communication can take place over this channel is characterized via information theory by the so-called multiaccess capacity region. A basic problem is developing coding schemes of relatively low complexity to achieve all rates in this capacity region. By exploiting the underlying geometrical structure of the capacity region, we develop a method of reducing the multi-user coding problem to a set of single-user coding problems using the ideas of time-sharing and successive decoding. Next...

‣ Coherent multi-photon interference and compensation of polarization dispersion

Fini, John Michael
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 233 p.; 1446327 bytes; 1446081 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
66.504053%
This thesis will explore strategies for coherent manipulation of multi-photon packets. Correlated multi-photon states can arise in nonlinear optical devices. A nonlinear quantum interferometer which includes these states can have interesting and strikingly different behavior from a conventional interferometer. The special quantum states set up in these devices are degraded by loss. In this thesis, we will set up theory for describing the interesting quantum behavior of these devices and the limitations imposed by loss decoherence. The underlying structure of interferometer states is shared by all two-mode systems-including classical polarization states of a single-mode fiber. We are exploring bire-fringent systems as a possible implementation of nonlinear quantum coupler ideas, but also because of its practical importance in optical communications. Polarization mode dispersion an important source of signal distortion in high-bitrate communications arising from unwanted birefringence in the fiber. We will describe theoretical analysis of compensated PMD systems, as well as our theoretical and experimental effeots to develop novel PMD compensators.; by John Michael Fini.; Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science...

‣ Multivariable analysis of spectral measurements for the characterization of semiconductor processes

White, David A. (David Allan), 1966-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 357 p.; 3990082 bytes; 3989731 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
66.504053%
The availability of affordable and reliable optical sensor technology and the abundance of data that these sensors now provide have created new opportunities to better characterize and control semiconductor processes in real-time. This thesis focuses on the analysis of multivariate methods and optical sensors for characterizing endpoint for two key processes: plasma etch and chemical mechanical polishing (CMP). To extract meaning information in real-time from the volumes of acquired optical sensor data, chemometric methods including principal component analysis (PCA) and partial least squares (PLS) are developed and tailored for characterizing endpoint and uniformity for each particular process. The results of this research include one of the first demonstrations of 1% low open area endpoint detection for a production etch process using a chemometrics-based estimator as well as comprehensive analysis and comparison of two innovative sensors, optical reflectance and IR thermography, for measuring wafer-level uniformity in CMP. During 8-inch copper polish experiments, the optical reflectance sensor is shown to demonstrate superior spatial resolution to IR thermography and provide spatial endpoint detection sufficient for reducing dishing and erosion during CMP. However...

‣ Development of a scintillating reference grid for spatial-phase-locked electron-beam lithography

Finlayson, Mark Alan, 1977-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 61 p.; 1649624 bytes; 1649424 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
66.504053%
by Mark Alan Finlayson.; Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2001.; Includes bibliographical references (p. 59-61).; This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.

‣ Development of X-ray lithography and nanofabrication techniques for III-V optical devices

Lim, Michael H. (Michael Hong)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 122 p.; 15749517 bytes; 15748992 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
66.504053%
This dissertation covers the development of fabrication techniques for Bragg-grating-based integrated optical devices in III-V materials. Work on this rich family of devices has largely been limited to numerical analysis because of the difficulties of their fabrication. The challenges of fabrication are addressed by dividing the problem along two lines: (1) development of an advanced x-ray mask system that addresses future nanolithography needs, and (2) development of fabrication techniques that addresses problems specific to Bragg-grating-based filters. A new x-ray mask configuration is described that improves many aspects of the x-ray mask. A novel means of measuring nondestructively x-ray mask distortion on a global scale was developed, called holographic phase-shifting interferometry (HPSI). This system, in conjunction with appropriate thermal input can potentially provide active correction of x-ray mask distortion. Current microphotonic fabrication issues are presented along with a detailed description of the dual-layer hardmask process (DLHP). The development of the DLHP was specifically geared towards the special requirements of Bragg-grating based microphotonics. Taken as a whole the author hopes that this dissertation serves to facilitate the building of advanced future integrated-optical devices.; by Michael Lim.; Thesis (Sc. D.)--Massachusetts Institute of Technology...

‣ Quantum signal processing

Eldar, Yonina Chana, 1973-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 346 p.; 3228057 bytes; 3227811 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
66.504053%
Quantum signal processing (QSP) as formulated in this thesis, borrows from the formalism and principles of quantum mechanics and some of its interesting axioms and constraints, leading to a novel paradigm for signal processing with applications in areas ranging from frame theory, quantization and sampling methods to detection, parameter estimation, covariance shaping and multiuser wireless communication systems. The QSP framework is aimed at developing new or modifying existing signal processing algorithms by drawing a parallel between quantum mechanical measurements and signal processing algorithms, and by exploiting the rich mathematical structure of quantum mechanics, but not requiring a physical implementation based on quantum mechanics. This framework provides a unifying conceptual structure for a variety of traditional processing techniques, and a precise mathematical setting for developing generalizations and extensions of algorithms. Emulating the probabilistic nature of quantum mechanics in the QSP framework gives rise to probabilistic and randomized algorithms. As an example we introduce a probabilistic quantizer and derive its statistical properties. Exploiting the concept of generalized quantum measurements we develop frame-theoretical analogues of various quantum-mechanical concepts and results...

‣ Design and implementation of an indoor mobile navigation system; CricketNav : design and implementation of a personal indoor navigation system

Miu, Allen Ka Lun, 1977-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 60 p.; 1777465 bytes; 1777221 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
66.504053%
by Allen Ka Lun Miu.; Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2002.; Includes bibliographical references (p. 59-60).; This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.

‣ A framework for multi-modal input in a pervasive computing environment

Agarwal, Shalini, 1979-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 62 leaves; 323495 bytes; 323228 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
66.504053%
by Shalini Agarwal.; Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2002.; Includes bibliographical references (leaves 51-53).; This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.

‣ A BiCMOS RF mixer for 5-GHz receivers; BiCMOS mixer for 5-GHz receivers

Baker, Michael W. (Michael Warren), 1977-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 119 leaves; 965632 bytes; 965393 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
66.504053%
by Michael W. Baker.; Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2002.; Includes bibliographical references (leaves 116-119).; This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.

‣ Diagnostic process monitoring with temporally uncertain models

Bull, Steven M. (Steven Michael), 1979-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 68 leaves; 300277 bytes; 300007 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
66.504053%
by Steven M. Bull.; Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2002.; Includes bibliographical references (leaves 67-68).; This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.

‣ Distributed construction of energy-efficient ad hoc wireless broadcast trees

Ahluwalia, Ashwinder S. (Ashwinder Singh), 1979-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 72 p.; 4610528 bytes; 4610283 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
66.504053%
by Ashwinder S. Ahluwalia.; Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2002.; Includes bibliographical references (p. 71-72).; This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.

‣ Rapid configuration of discourse and dialog management in conversational systems

Crockett, Sterling J. (Sterling John), 1976-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 80 p.; 497443 bytes; 497196 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
66.504053%
by Sterling J. Crockett.; Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2002.; Includes bibliographical references (p. 70).; This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.

‣ Design of a low power capacitive sensor for a micromachined accelerometer

Good, Daniel (Daniel Albert), 1979-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 73 leaves; 346548 bytes; 346283 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
66.504053%
by Daniel Good.; Thesis (M.Eng. and S.B.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2002.; Includes bibliographical references (leaves 72-73).; This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.

‣ Utility functions for ceteris paribus preferences

McGeachie, Michael J
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 103 p.; 530454 bytes; 530140 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
66.504053%
by Michael McGeachie.; Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2002.; Includes bibliographical references (p. 101-103).; This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.

‣ Subgradient methods for convex minimization

Nedić, Angelia
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 174 p.; 1040674 bytes; 1040074 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
66.504053%
Many optimization problems arising in various applications require minimization of an objective cost function that is convex but not differentiable. Such a minimization arises, for example, in model construction, system identification, neural networks, pattern classification, and various assignment, scheduling, and allocation problems. To solve convex but not differentiable problems, we have to employ special methods that can work in the absence of differentiability, while taking the advantage of convexity and possibly other special structures that our minimization problem may possess. In this thesis, we propose and analyze some new methods that can solve convex (not necessarily differentiable) problems. In particular, we consider two classes of methods: incremental and variable metric.; by Angelia Nedić.; Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2002.; Includes bibliographical references (p. 169-174).; This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.

‣ Exploiting E-mail structure to improve summarization

Lam, Derek Scott, 1979-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 81 p.; 310153 bytes; 309910 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
66.504053%
by Derek Scott Lam.; Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2002.; Includes bibliographical references (p. 77-81).; This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.

‣ Extending the Java language for the prevention of data races

Lee, Robert Honway, 1981-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 82 p.; 430125 bytes; 429805 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
66.504053%
by Robert Honway Lee.; Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2002.; Includes bibliographical references (p. 81-82).; This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.